MAGNETORESISTANCE AND MAGNETIZATION STUDIES OF ND1-XCU3O7-DELTA SINGLE-CRYSTALS(XBA2)

We have studied the magnetotransport and magnetization properties of N d1+xBa2-xCu3O7-delta single crystals grown by the traveling-solvent fl oating-zone technique under controlled O-2 atmosphere. A magnetic phas e diagram has been established from both of the above methods. The mag netic relaxation measurements in the remnant state reveal a plateau in the relaxation rate and in the pinning energy over a temperature rang e 30 to 60 K, This suggests a distribution of pinning potentials produ ced by Nd/Ba substitution which could act as effective pinning centres homogeneously distributed in the crystal. These are finely dispersed in either the weak or non-superconducting phase which grows into poten tial pinning centres in high fields as well as the high temperature re gion. The sites display some sort of preferential pinning parallel to the c-axis. Our results suggest that Nd/Ba substitution can be potenti al pinning centres if conditions are optimized.